Vehicle bumper

ABSTRACT

A shock-absorbing bumper comprises a semi-rigid resilient fascia and a bumper bar spaced rearwardly from the fascia, the space therebetween being filled with an integral skin urethane foam which is resiliently compressible and integrally bonded to the fascia and bumper bar.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 624,202, filed June 24, 1984,now U.S. Pat. No. 4,616,866, which is a continuation-in-part ofapplication Ser. No. 568,215, filed on Dec. 30, 1983, now abandoned.

TECHNICAL FIELD

This invention relates to an energy-absorbing bumper for vehicles.

BACKGROUND ART

In recent years various designs of vehicle bumpers have been proposedthat are intended to absorb moderate impact forces without damage to thebumper or the vehicle on which it is mounted. One approach has been touse fluid shock-absorbers mounted on the chassis of the vehicle. In thecase of bumpers made of plastic, some are in the form of a molded hollowfascia with a molded plastic back-up member or bar linear welded orotherwise secured mechanically to the fascia. In some such bumpers aplastic foam member is inserted between the fascia and the back-upmember, the back-up member providing a means for mounting the bumper onthe frame of a vehicle. See, e.g. U.S. Pat. Nos. 3,721,433; 3,860,279;3,866,963, 4,106,804; 4,109,951; 4,116,983; 4,134,610; 4,213,644;4,268,079; 4,325,574; 4,328,986; 4,350,378; and 4,361,352.

While these and other types of bumpers made wholly or partially ofplastic compositions do provide some degree of energy absorption, theyare costly to manufacture and assemble, but, in addition, experience hasshown that their ability to absorb forces encountered in a relativelymoderate impact is, in many instances, insufficient to prevent damage tothe bumper or the vehicle.

DISCLOSURE OF THE INVENTION

The present invention has for its primary object the provision of avehicle bumper capable of absorbing greater impact forces without damageto the bumper or to the vehicle.

Another object of this invention is to provide a shock-absorbing bumperthat can be manufactured and assembled economically.

Still another object of this invention is to provide a shock-absorbingbumper with sufficient energy management capability to avoid the needfor use of fluid shock absorber devices in some cases.

More specifically, the present contemplates a bumper having a semi-rigidresilient fascia, preferably molded from plastic, and a back-up ormounting member for the bumper spaced from the front face of the fascia,the space therebetween being filled with a resiliently compressible,integral skin plastic foam member molded in situ and integrally bondedto the fascia and the back-up or mounting member. In the bumper of thepresent invention the increased energy absorption is attributedprimarily to the compressibility of the foam core, the adhesion of theintegral skin of the foam core to the bumper members and the elongationand tear strength of the integral skin in tension. When a bumper of thepresent invention is subjected to an impact force, the fascia isdeformed and the foam core is compressed. This introduces tension insections of the foam core and the integral skin. Since the foam isadhered to the bumper elements, this tension tends to inhibitdeformation and, thus, increases the energy absorbed by the bumperitself through rearward and lateral distribution of the impact loadthroughout the bumper.

Another advantage of the present invention is that the bumper maintainsits shape and dimensional integrity when heated in a painting process.

Other objects, features and advantages of the present invention willbecome apparent from the following description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 and 10 are vertical sectional views of various embodiments ofbumpers according to the present invention, the upper section of eachview showing the bumper components in their normal position and thelower section showing the bumper components in the impacted condition;

FIGS. 6, 7, 8 and 11 are sectional views showing further modificationsof the present invention; and

FIG. 9 is a fragmentary horizontal sectional view of another embodimentaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, the bumper there illustrated comprises a fasciamember 10 formed to have a generally U-shaped front portion 12 and upperand lower flanges 14 extending rearwardly from the front portion. Abumper bar 16 extends substantially the full length of fascia 10 and isjoined to flanges 14, such as by a linear weld, at 18. The volumebetween the front portion 12 of the fascia 10 and bumper bar 16comprises plastic foam. The foam is molded in situ by positioning thefascia 10 and the bumper bar 16 in the desired spaced relationship andintroducing the foam in the volume which is bounded, in at leastsubstantial part by the fascia and bumper bar. Surface area not boundedby the fascia and bumper bar are bounded by core pieces of shapesselected to provide the desired configuration of the exposed foam area.The core pieces are pre-treated with mold release materials. A foamableplastic is introduced into the volume and allowed to expand and thencure to a semi-rigid state of desired resilience and compressibility.The foam is preferably a resiliently flexible urethane foam which cureswith an integral skin. The interior surfaces of the fascia 10 and thebumper bar 16 may be prepared prior to the introduction of the foamableplastic to enhance bonding. Depending on the materials selected, suchsurface preparation may involve adhesive application, flame treatment,priming and the like.

Thus, the foam member 20 has a resiliently compressible core 22 and anintegral skin 24. Fascia 10 and bumper bar 16 are formed of materials towhich the foam member 20 securely adheres when molded therein. Theintegral skin 24 on the foam core 22 and the tenacious bond between theskin 24 and the adjacent surfaces of members 10 and 16 are criticalfeatures of the present invention. As pointed out above, when the bumperis mounted on the frame of a vehicle, such as by the bolts 26, and issubjected to an impact force, the localized area of the fascia where theforce is applied deforms generally to the configuration shown in thelower portion of FIG. 1. The central portion of the foam core 22compresses as indicated at 22' and, since the bumper bar 16 is fixedlysecured to flanges 14, the rounded front portion 12 of the fascia 10 isdistorted into a flat vertical section 12'. The flattening of the frontface causes its upper and lower portions to flare outwardly in avertical direction as indicated at 12'. The compression of the foam core22 will absorb a considerable portion of the impact energy, but, at thesame time, the energy absorption is increased by the fact that portionsof the skin 24 bonded to the fascia 10 are placed in tension. Thestretching or elongation of the higher density integral skin 24 absorbsadditional impact energy and this tension tends to inhibit deformationof the fascia, thus further increasing the energy absorption. Inaddition, the tension in the skin tends to return the fascia to itsoriginal contour.

The bumper illustrated in FIG. 2 differs only slightly from thatillustrated in FIG. 1 in that the junction between front portion 12 andflanges 14 is formed as a V-shaped notch 28 in which the forwardlyextending flanges 29 of the bumper bar are engaged to mechanicallyinterlock fascia 10 and bumper bar 16. This connection serves generallythe same function as linear welds 18 in that it prevents the fascia as awhole from shifting rearwardly relative to bumper bar 16 and preventsthe flanges 14 from flaring vertically when an impact force is appliedto the bumper. However, in this embodiment (as will be seen to be truealso for the embodiments of FIGS. 3-6, 8, 10 and 11) the bumper bar canbe formed of a non-plastic material, e.g. steel, as many plastic foamsadhere well to metal. Foam member with the integral skin 24 absorbsimpact forces applied to the bumper in substantially the same manner asdescribed above with respect to FIG. 1.

In the bumper illustrated in FIG. 3 flanges 14 of fascia 10 are slidablyengaged with the opposite flanged ends of bumper bar 16 so that, uponimpact, the fascia as a whole can shift rearwardly relative to thebumper bar. When an impact occurs the form core 22 is compressed as at22' and the upper and lower portions thereof are extruded outwardly andrearwardly as at 22'. This causes the integral skin 24 adjacent theoutwardly flared portions 14' of the fascia to stretch. In order toinhibit tearing of the foam and skin a mold release compound is appliedto the inner face of the fascia along the areas designated 30.

In the arrangements illustrated in FIGS. 2 and 3 and in the arrangementshereinafter described the fascia and the back-up member or the bumperbar are held in assembled relation solely by the bond between theintegral skin on the foam core and bumper bar. This reduces considerablythe cost of manufacturing and assembling the complete bumper. Theconstruction shown in FIG. 3 can be employed on those vehicles whererearward displacement and vertical flaring of the flanges 14 of thefascia do not interfere with other components of the vehicle frame orbody.

In the arrangement illustrated in FIG. 4 the bumper bar 16 is formedwith openings or apertures 32 and the foam member 20 is initially moldedso that an extrudate extends through the openings 32 and adheres to theinner faces of flanges 14 as indicated at 34. A release compound isapplied to the areas 35 at openings 32. Upon impact the portions 36 ofthe foam member 20, including the integral skin thereon, becomestretched as shown in the lower portion of FIG. 4. This reduces theextent to which the flanges 14 will flare vertically and also increasesthe amount of energy absorbed upon impact since a portion of this energyis utilized to stretch the portion 36 and the integral skin thereon.

In the case of the exposed surface of the extrudate in the embodiment ofFIG. 4, and in other embodiments in which surface portions of the foamare exposed, the exposed areas may be sealed with an elastomeric sealer,such as by spraying or dipping, to make the exposed areas impervious tothe entry of water.

In the event there is a tendency for the skin and foam to shear in thesections 22" of the arrangement shown in FIG. 3, this can be reduced toa large extent by the arrangement shown in FIG. 5. Stated differently,the arrangement shown in FIG. 5 is capable of withstanding a higherimpact load without shearing the foam member 20. In the bumper shown inFIG. 5 the fascia 38 has a flat front portion 40, as distinguished fromthe rounded portion 12 of the fascia 10 illustrated in FIGS. 1 through4. This difference is merely one of ornamentation and does not affectthe energy absorbing properties of the bumper. However, in the bumpershown in FIG. 5 the bumper bar 16 terminates along its upper and loweredges inwardly of the flanges 14 of the fascia and the foam member 20 ismolded between the fascia and the bumper bar so that it extendsrearwardly beyond the bumper bar 16 along the upper and lower edgesthereof as indicated at 42. The vertical spacing between the bumper bar16 and the flanges 14 tend to minimize vertical displacement of theflanges on impact of the bumper. When the front face of the fascia issubjected to an impact the foam core is compressed as at 22' and theportions 42, together with the integral skin thereon, are stretched intothe configuration shown at 42'. As in the previous embodimentsdescribed, the presence of the integral skin on the foam core and itsadherence to the bumper members absorbs a very substantial portion ofthe impact energy without damaging the bumper. The tension developed inthe core and the integral skin also tends to return the fascia to itsoriginal configuration after the impact force is released.

The arrangement shown in FIG. 6 is somewhat similar to that shown inFIG. 5 except that the bumper bar 44 is formed as a hollow memberextending substantially the full length of the bumper. Bumper bar 44 canbe extruded from a semi-rigid plastic or can be formed from a somewhatresilient sheet material. In either event, the bumper bar has theintegral skin foam 46 molded therein simultaneously with the molding ofthe foam member 20 in the fascia. The integral skin foam 46 may beselected to have different compressibility than the foam 20 as anothermeans of managing the absorption and distribution of impact loads to thefascia 10. Thus, the bumper bar 44 and the fascia 10 are held inassembled relation by the integral skin 24 of the foam member 20. Theportions 42 of the foam member 20 which project rearwardly from theupper and lower edges of bumper bar 44 serve the same purpose as theportions 42 illustrated in FIG. 5. The hollow bumper bar increases thesection modulus and further enhances the energy absorbingcharacteristics of the bumper.

In the arrangement shown in FIG. 7 the bumper bars previously shown anddescribed are replaced by a thin metal tension strap 48 which extendslengthwise of the bumper at least between the two bumper mountingcolumns or brackets (not shown) on the vehicle frame. The tension strap48 is formed with a plurality of openings 50 therein and the foam member20 is molded in situ so that the tension strap 48 is substantiallycompletely embedded in the foam except at the area surrounding themounting screws 26. As in the arrangements illustrated in FIGS. 5 and 6,the tension strap 48 and the fascia 10 are held together solely by theintegral skin 24 on the foam member 20. Likewise, as in FIGS. 5 and 6,foam member 20 extends rearwardly beyond the upper and lower edges ofthe tension strap 48 as at 52. By encapsulating strap 48 within the foammember 20 a more secure bond between these members is obtained. It maybe advantageous to prepare the surface of the strap 48 to enhanceadhesion.

In the bumper illustrated in FIG. 8 the bumper bar 54 is completelyembedded in the foam member 20 and the upper and lower edges which arespaced from the flanges of the fascia are inclined rearwardly as at 56.With this arrangement, when the fascia is subjected to an impact force,the vertical central portion 58 of the foam member 20 is subjected tocompression, but, at the portions 60 of foam member 20 adjacent therearwardly inclined portions 56, the forces on the foam member 20 aregradually converted from compression forces to tension forces. Thus,these rearwardly inclined portions avoid an abrupt change fromcompresson to tension forces in the member 20 and further inhibittearing of the foam at these sections. There is also illustrated in FIG.8 one of the two mounting columns or brackets 62 on the vehicle frame onwhich the bumper is mounted. In addition to the bumper bar 54, FIG. 8shows the use of a separate thin metal tapping plate 64 at each of thetwo mounting points of the bumper bar on the vehicle frame.

FIG. 9 illustrates a special application of the bumper of the presentinvention wherein the bumper is adapted for mounting on a vehiclealready equipped with a backing member. Specifically, this embodimentutilizes individual metal tapping plates 64 embedded in the foam member20 and located adjacent each of the mounting brackets for mounting thebumper on the vehicle frame. In this arrangement a metal strap 66extending between the two bumper mounting brackets on the vehicle framefunctions to provide the required backup for compression of the foam 20.The strap 66 has two spacers 68 secured thereto as by welding (as at70). In this arrangement the bumper itself simply consists of the fascia10, the foam member 20 and the two tapping plates 64 encapsulated in thefoam as illustrated.

FIG. 10 shows another embodiment of the invention with the addedfeatures of a rib 72 formed integrally with the bumper bar 16. The viewalso shows the foam 20 forwardly recessed in the area 74 proximate thevertical extreme of the bumper bar.

The rib 72 is formed as an integral extension of the bumper bar 16 toadd rigidity. In its relaxed state it can be canted relative to thevertical dimension of the bumper bar to facilitate deflection uponimpact of the fascia 10 as shown in FIG. 10.

The recess in area 74 provides another compression and flow pattern forthe plastic foam 20 to absorb and distribute impact loads to the fascia10.

FIG. 11 is a cross-sectional view of another bumper embodimentillustrating two additional features of the present invention. Thesection or cutting plane line of FIG. 11 is offset at the verticalmidpoint of the bumper to show the interruption of foam skin proximatethe fastener.

First, the lower flange 14 of the fascia 10 is shown projecting in agenerally downward direction forward of the bumper bar 16.

Second, the foam is made of two constituents to give it a cross-sectionof varying density and rigidity. That is, in the embodiment of FIG. 11,a pre-molded plastic foam bun 76 of one desired density or rigidity isembedded within a foam matrix 78 molded in situ and of another densityor rigidity. This feature of varying cross-sectional density of the foamgives added control over the energy management. The invention alsocontemplates the same result achieved by using a homogenous plastic foamof continuously varying or graduated density across the cross-sectionalarea of the foam.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A vehicle bumpercomprising:a fascia adapted to receive impact forces; a backing memberpositioned rearwardly of the fascia; and a resiliently compressibleplastic foam molded in situ in the volume bounded on the front by thefascia and on the rear by the backing member, said foam having anintegral skin bonded to adjacent surfaces of the fascia and the backingmember.
 2. A vehicle bumper comprising:a fascia having a front portionadapted to receive impact forces and upper and lower flanges extendingrearwardly from said front portion; and energy management meanspositioned rearward of said fascia and formed, at least in part, insitu, for responding to impact forces transmitted by the fascia bycontrolled resilient compression and exhibiting tension in an integralskin bonded to the interior surface of the fascia of the portion formedin situ.
 3. The vehicle bumper as defined in claim 2 wherein the energymanagement means includes a resiliently compressible plastic foam havingan integral skin bonded to the interior surface of the fascia.
 4. Aprocess for forming a vehicle bumper comprising the steps of:positioninga fascia having a front portion and upper and lower flanges extendingrearwardly therefrom in a predetermined spaced relation to a rearbacking member to define a volume bound, in substantial part, by saidfascia and said backing member; molding in situ a resilientlycompressible plastic foam in substantially all of said volume; andcuring the plastic foam to form an integral skin bonded to adjacentsurfaces of the fascia and the backing member.
 5. The process of claim 4comprising the intermediate step of introducing a pre-molded plasticfoam bun of a first density into said volume, and wherein the plasticfoam molded in situ is of a second density.
 6. The process of claim 4further comprising the initial steps of forming the fascia and thebacking member.
 7. The process of claim 6 wherein the fascia and thebacking member are injection molded.
 8. The process of claim 6 furthercomprising:forming the backing member with at least one aperturetherein, and molding the plastic foam to include an extrudate extendingthrough and rearward of said backing member.
 9. The process of claim 6wherein the backing member is formed to have a channel shape with aninternal volume therewithin, and the molding step involves the in situfilling of substantially all of the internal volume of the channel witha resiliently compressible plastic foam.
 10. The process of claim 9wherein the molding step involves filling the volume interior to thechannel with a foam of different density than that molded in situexterior of the channel volume.
 11. The process as defined in claim 4comprising the further step of forming the backing member with anintegral forwardly projecting rib.
 12. The process of claim 4 whereinthe molding step further comprises embedding the backing member in saidfoam.
 13. The process of claim 12 wherein the backing member is formedto have rearwardly extending terminal segments.
 14. The process of claim4 wherein the backing member is positioned in spaced vertical relationto the upper and lower flanges of said fascia and further wherein theplastic foam is molded to include integral portions extending throughthe vertical spaces between the backing member and the fascia.
 15. Theprocess of claim 4 wherein the backing member is positioned in spacedvertical relation to the upper and lower flanges of said fascia, andfurther wherein the plastic foam is molded to have a recessed portionproximate the vertical space at the upper and lower ends of the backingmember.
 16. The process of claim 4 further comprising the intermediatestep of preparing the interior surfaces of the fascia and the backingmember to enhance bonding of the plastic foam to said surfaces.
 17. Theprocess of claim 4 further comprising the step of sealing any exposedsurface portions of the resiliently compressible plastic foam.
 18. Thevehicle bumper of claim 3 wherein the energy management means furtherincludes a backing member positioned rearwardly of the fascia and bondedto the integral skin of the foam.
 19. The vehicle bumper of claim 18wherein the backing member includes one or more ribs orientedtransversly to the front portion of the fascia.
 20. The vehicle bumperof claim 19 wherein said one or more ribs are formed integrally with thebacking member.